The present invention relates to an assay tray assembly. It is particularly concerned with an assembly for use in the testing or analysis of liquids, usually of a chemical, bio-chemical or biological nature, by a batch process whereby multiple small quantities of the liquid or liquids under test can be prepared for analysis substantially simultaneously, the process conveniently being carried out by conventional mechanical handling equipment. Assemblies of the kind mentioned include an separation medium to which the liquid for analysis is subjected; this medium may simply serve to remove solid/particulate matter from the liquid by filtration or may be in the form of chromatographic medium having a selectively adsorbent nature intended to separate or indicate a particular characteristic (or the lack of such a characteristic) of the liquid under test.
Particularly in chemical and pharmaceutical research there is a large demand for the assay or analysis of small quantities of liquid by chromatographic techniques and it has hitherto been proposed to provide array trays and assemblies whereby individual samples of test liquid are prepared for and subjected to analysis by multi-batch processing on a microtiter principle, for example as disclosed in EP-A-2-0087899 in which samples of a reaction medium are carried by a spaced array of downwardly extending rods which rods and samples are inserted, one each, into a corresponding array of discrete wells containing the test liquid. An assay tray assembly for similar batch processing is also disclosed in U.K. Patent Specification No. 2,188,418A in which a base tray has a plurality of reaction wells and an overlying tray has a corresponding number of solid or hollow reaction projections either or both of which may carry a reaction medium that provides a basis for analysis when the reaction projections are inserted into the corresponding reaction wells containing the test liquid.
A conventional assay technique is to locate the separation medium in an upstanding tubular chamber having an open top and a bottom outlet and to pipette or otherwise deposit the liquid under test into the chamber to flow through or over the extraction medium prior to emerging from the bottom outlet. Conventionally this type of analysis is made on an individual basis, for example by use of an extraction cartridge sold under the Trade Mark BOND ELUT which comprises a tubular plastics body carried within which is a predetermined chromatographic medium. Such individual cartridges have been found inappropriate in trying to achieve a high through put of test samples for analysis. It has however been proposed, in U.S. Pat. No. 4,090,850 to provide an assay unit (particularly for radio-immunio assay) which utilizes a batch process whereby a tray is provided with multiple wells each having at its bottom an outlet communicating with a vacuum chamber. Each well carries an extraction medium so that liquid under test deposited in each well flows through the extraction medium and the percolate or eluate, as the case may be, passes by way of the outlets into the vacuum chamber which acts as a common waste reservoir. By exhausting the vacuum chamber the liquids in the wells are subjected to a pressure differential to increase the rate of through-flow for the analysis procedure.
With assay techniques in which there is a flow of liquid under test through or over a separation medium as previously discussed, it is frequently important that the liquid emerging from the separation medium is available for discrete analysis, possibly as an alternative, or addition, to the analysis of the separation medium. If such a facility is to be provided in the assaying of liquids by use of a batch technique, it is essential that there is no intermixture or cross contamination between the liquids emerging from the individual outlets of the several chambers which accommodate the separation medium. It is an object of the present invention to provide an assay tray assembly by which this requirement may be satisfied and which may be produced relatively inexpensively for one-lime or repeated use, is convenient to use, and lends itself to mechanical handling and processing, for example with apparatus having an automatic bulk dispensing and aspirating capability.